1. Field of the Invention
The present invention relates to an aqueous dispersion for chemical mechanical polishing. More specifically, the invention relates to an aqueous dispersion that is particularly useful for chemical mechanical polishing of metal layers during production steps for semiconductor devices.
2. Description of the Prior Art
Improvements in degrees of semiconductor device integration and increased multilayer wiring have led to the introduction of chemical mechanical polishing (hereunder referred to as xe2x80x9cCMPxe2x80x9d) techniques for polishing of working films and the like. As disclosed in Japanese Laid-open Patent Publication No. Sho-62 -102543, No. Sho-64-55845 and No. Hei-5-275366, Published Japanese translations of PCT international publication for patent applications No. Hei-8-510437, and Japanese Laid-open Patent Publication No. Hei-8-17831, No. Hei-8-197414 and No. Hei-10-44047, there are employed methods whereby wiring is formed by embedding a wiring material such as tungsten, aluminum or copper in a hole or trench formed in the insulation film of a process wafer, and then removing the excess wiring material by CMP.
In this CMP process, the chemical etching and mechanical polishing must be effectively incorporated together and the balance between the chemical function and mechanical function is important for obtaining a polished surface with sufficiently high precision.
Many types of aqueous dispersions have been proposed as compositions for CMP, and in recent years particular emphasis has been on improving the chemical etching function. For example, in Japanese Patent Publication No. Hei-6-103681 there is disclosed a polishing composition comprising abrasive particles, a transitional chelate salt and a solvent that dissolves the salt. In Japanese Laid-open Patent Publication No. Hei-6-313164 there is disclosed a polishing composition composed of a polishing material comprising an aqueous colloidal silica sol or gel and a polishing accelerator comprising a persulfuric acid salt. In Japanese Laid-open Patent Publication No. Hei-7-233485 there is described a polishing composition containing aminoacetic acid, amidosulfuric acid, an oxidizing agent and water. In Japanese Laid-open Patent Publication No. Hei-11-135467 there is described a polishing composition containing a tetravalent cerium salt in aqueous solution. In Japanese Laid-open Patent Publication No. Hei-10-265766 there is described a polishing composition comprising a combination of hydrogen peroxide and a catalytic amount of iron ion. However, while these polishing compositions all have greater chemical etching ability and higher removal rates, the balance with the mechanical polishing ability is insufficient, such that the wiring materials undergo excessive etching, corrosion traces are left on the polishing surfaces, and dishing, thinning and keyholes are produced on plug surfaces, creating a problem in that satisfactory finished surfaces cannot be obtained.
The mechanical polishing ability depends largely on the abrasive, and inorganic particles such as silica and alumina particles have been commonly used in the prior art. Such inorganic particles must be stably dispersed in a slurry, but problems such as instability and aggregate formation sometimes occur because of reduced colloid stability due to additives such as polishing accelerators, sedimentation in a slurry during storage, and the like. The aggregates produce nicks (scratches) in the polishing surface, and this leads to reduced yields. However, no aqueous dispersion for CMP has yet been proposed that provides both the chemical etching ability described above and stability of the abrasive in the aqueous dispersion.
The present invention is aimed at overcoming the aforementioned problems of the prior art, and it provides an aqueous dispersion for CMP that has an excellent balance between chemical etching and mechanical polishing ability. That is, the object of the present invention is to provide an aqueous dispersion for CMP with a high removal rate that allows efficient polishing, while also producing minimal excessive etching, thinning, dishing, keyholes and scratches, to give finished surfaces with satisfactory high precision.
According to the present invention, an aqueous dispersion for CMP having constitution described below is provided to solve the above-mentioned objects.
[1] An aqueous dispersion for chemical mechanical polishing characterized by comprising an abrasive, water and a heteropolyacid.
[2] An aqueous dispersion for chemical mechanical polishing according to [1] above, characterized in that said heteropolyacid is at least one selected from among silicomolybdic acid, phosphorotungstic acid, silicotungstic acid, phosphoromolybdic acid and silicotungstomolybdic acid.
[3] An aqueous dispersion for chemical mechanical polishing according to [1] above, characterized by being used for polishing of a polishing surface with a tungsten film.
[4] An aqueous dispersion for chemical mechanical polishing according to [1] above, characterized by being used for polishing of a polishing surface with at least one from among copper films, aluminum films, ruthenium films, tantalum films, titanium films and platinum films.
[5] An aqueous dispersion for chemical mechanical polishing according to [1] above, characterized in that upon contact with the metal layer of a polishing surface, the etching rate of said metal layer is 100 xc3x85/min or less.
[6] An aqueous dispersion for chemical mechanical polishing, characterized by comprising an abrasive, water, a heteropolyacid and an organic acid.
[7] An aqueous dispersion for chemical mechanical polishing according to [6] above, characterized in that said heteropolyacid is at least one selected from among silicomolybdic acid, phosphorotungstic acid, silicotungstic acid, phosphoromolybdic acid and silicotungstomolybdic acid.
[8] An aqueous dispersion for chemical mechanical polishing according to [6] above, characterized in that said organic acid has two or more carboxyl groups in one molecule.
[9] An aqueous dispersion for chemical mechanical polishing according to [8] above, characterized in that said organic acid is at least one selected from among oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid, phthalic acid, malic acid, tartaric acid and citric acid.
[10] An aqueous dispersion for chemical mechanical polishing according to [6] above, characterized by being used for polishing of a polishing surface with a tungsten film.
[11] An aqueous dispersion for chemical mechanical polishing according to [6] above, characterized by being used for polishing of a polishing surface with at least one from among copper films, aluminum films, ruthenium films, tantalum films, titanium films and platinum films.
[12] An aqueous dispersion for chemical mechanical polishing, characterized by comprising colloidal silica with a primary particle size of 5-100 nm, water and a heteropolyacid.
[13] An aqueous dispersion for chemical mechanical polishing according to [12] above, characterized in that said colloidal silica is colloidal silica obtained by hydrolysis and condensation from an alkoxysilane.
[14] An aqueous dispersion for chemical mechanical polishing according to [12] above, characterized in that said heteropolyacid is at least one selected from among silicomolybdic acid, phosphorotungstic acid, silicotungstic acid, phosphoromolybdic acid and silicotungstomolybdic acid.
[15] An aqueous dispersion for chemical mechanical polishing according to [12] above, characterized by further comprising an organic acid.
[16] An aqueous dispersion for chemical mechanical polishing according to [12] above, characterized by being used for polishing of a polishing surface with a tungsten film.
[17] An aqueous dispersion for chemical mechanical polishing according to [12] above, characterized by being used for polishing of a polishing surface with at least one from among copper films, aluminum films, ruthenium films, tantalum films, titanium films and platinum films.
The aqueous dispersion for CMP according to the invention has an excellent balance between chemical etching and mechanical polishing ability, and when used for polishing of polishing surfaces with metal layers it can give highly precise polished surfaces with no corrosion, dishing or keyholes on the polished surfaces. The aqueous dispersion for CMP according to the invention is therefore useful for CMP of polished surfaces with metal layers in manufacturing processes for semiconductor devices.